A biofilm is build up by microorganisms. In a biofilm, microbial cells stick to each other and/or to a surface. These cells generally resemble adherent cells which are often embedded within a self-produced matrix of extracellular polymeric substance (EPS). The self-produced matrix of extracellular polymeric substance can also be designated as microbial slime. It is a polymeric conglomeration generally composed of extracellular DNA, proteins, and/or polysaccharides. Microorganisms form a biofilm in response to many factors, which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or by exposure to specific molecules and/or stimuli. When a cell switches to the biofilm mode of growth, it undergoes a phenotypic shift in behavior in which several genes are differently regulated.
Biofilms preferentially develop on inert surfaces including those of everyday and household items as well as on medical devices. Biofilms may form on polymeric materials, metals, glass, and ceramics, among others. Exposure to such microorganisms for instance through skin-surface contact may result in infections that compromise the health. Biofilms may form on any number of items with which persons come into contact such as: hygiene products, medical devices, household appliances, tap ware and so forth. Controlling formation of biofilms could result in less infection of individuals.
Biofilm formation has further important public health implications. Drinking water systems and waste water systems are known to harbor biofilms, even though these environments often contain disinfectants. Any system providing an interface between a surface and a fluid or gas has the potential for biofilm development. Ventilation systems as well as air condition systems such as water cooling towers for air conditioners are well-known to pose public health risks from biofilm formation, as episodic outbreaks of infections caused by Legionella attest. Turbulent fluid flow over the surface does not provide protection. Biofilms can form in conduits where flowing water or other fluids pass, with the effects of altering flow characteristics and passing planktonic organisms downstream. Industrial fluid processing operations have experienced mechanical blockages, impedance of heat transfer processes, and biodeterioration of fluid-based industrial products, all attributable to biofilms. Biofilms have been identified in flow conduits such as hemodialysis tubing, and in water distribution conduits. Biofilms have also been identified to cause biofouling in selected municipal water storage tanks, private wells and drip irrigation systems.
Microbial infection, and the subsequent formation of biofilms remains one of the most serious complications in several areas, particularly in medical devices, drugs, health care and hygienic applications, drinking water systems, water purification systems, hospital and dental surgery equipment, textiles, food packaging and food storage systems. Since the difficulties associated with eliminating biofilm-based infections are well-recognized, a number of agents have been tested to treat surfaces or fluids bathing surfaces to prevent or impair biofilm formation.
Preventing or impairing biofilm formation by undesirable microorganisms traditionally requires the use of dispersants, surfactants, enzymes, antimicrobial agents, biocides, specific metals, and/or chemicals. However, the agents for preventing or impairing biofilm formation on the market, e.g. antimicrobial agents or metals such as silver, have been reported to be expensive, not permanent, harmful to health, harmful to the environment, and to require a laborious process for their manufacture and application. In addition, many agents used in this context cannot be sterilized. Antibiotics, for example, are often not active anymore after undergoing sterilization processes. Moreover, many agents for preventing or impairing biofilm formation, e.g. chemical additives, are not suitable in medical applications in view of their side effects. In addition, any agent used to prevent or impair biofilm formation that will be exposed to individuals must be safe to the user. Certain biocidal agents, in quantities sufficient to interfere with biofilms, also can damage host tissues. Thus, it is advantageous for the biofilm resistant compound to function not as a biocide, but to render surfaces unsuitable for adhesion and colonization by microorganisms. Such a compound does not rely on a “kill mechanism” for the prevention of biofilms, but on creating an environment not conducive to biofilm formation.
Based on the above, there is a need for new agents/substrates which can be used for preventing or impairing biofilm formation, e.g. agents/substrates, which are cost-effective, stable, sterilizable, safe, and free of side effects. Natural substances or nature-identical substances for this purpose would be highly desirable as they are usually well tolerated by human beings and animals. However, such natural substances usually resemble perfect breeding soils for microbes—resulting in the opposite of the desired effect.
The inventors of the present invention surprisingly found a biopolymer which has the above-mentioned properties and which is, thus, very suitable for the avoidance or reduction of biofilm formation. They surprisingly found that biofilm formation can be avoided or reduced by coating a surface of a substrate with the biopolymer or by incorporating the biopolymer into a substrate as a whole. The mechanism by which the present invention prolongates/hinders the formation and growth of biofilms is by creating a surface with the biopolymer, wherein microorganisms associated with biofilms do not readily adhere or colonize.